First off, search engine friendly is not the same as search engine optimized!
This is something Joost de Valk already wrote about in his post Search Engine Friendly vs Search Engine Optimized

Search engine optimization does go a lot further then making a search engine friendly website, and building a Content Management system for websites that is search engine optimized…, that is just not possible…

What is possible is to look at the search engine friendliness of three popular Open Source CM systems.
Basics for this comparison are the options necessary that are in the system itself and not those things that can by done with Content, Images, Layout or other aspects.
So no info about H1 or H2, no alt or title tags for images and more.
No, you can read here about:

• The possibility to influence the HTML title separate from the content title
• The possibility to use the Metatags like Description and Keywords on individual content items
• Create search engine friendly URLs, preferably with keywords in it, or other wise with as little possible use of parameters like id_?=12 or similar.

For all three system's the comparison is with the following technical hosting specification:

• Linux (UNIX) based hosting
• PHP 4 or PHP 5
• Apache webserver with Mod_Rewrite active

WordPress, Drupal en Joomla

WordPress

• URL Rewrite is easy to realize with the “Permalink” option, WordPress can set the right .htaccess options in the file if the file is writable. My own mostly used option is to use the custom option /%postname%/ with which the post title is also the URL. You can change the URL by changing the text in the “Post Slug” option.
• Title is naturally  the standard title of your post, but you want more control on the option for search engine, that is why your could use the  SEO Title tag plugin with just a minor change in your template.
• Metatags in a basic WordPress installation there is no possibility to change the “Description” and “Keywords” per post or page. With the All-in-one-SEO-Pack plugin you will have all these options. You can also change the Title with this plugin, but I like the overview and options that SEO Title tag will give you.
  You can use both plugins at the same time if you disable the title rewrite option in All-in-one-SEO-Pack

Tip: Use the optional excerpt function to generate the Meta description, that will also give you better archive pages, since most of the templates use that data for the archive page creation.

Drupal

• URL rewrite in Drupal you need to use the site configuration option “Clean URLs” that also can change your .htaccess file if it is writable. But that just changes your URL to /node/1/ instead off q=1. And you need more…. That is why you need to install the “pathauto” module and you activate the modules “path” and “pathauto”.
• Title this is just as with the other just the title of your content item, but with the Page Title module you just have a little more control about the title tag, but not a lot.
• Metatags in the standard installation of Drupal this option is also not available, but with the Meta Tags Nodeword module you will get that possibility.

Tip: Set in the Pathauto module in the general settings the option at “Update action” to “Do Nothing” with this option you will later have the possibility to change the title without changing the URL.

Joomla 1.0

• URL rewrite in version 1.0.x of Joomla there is an SEO option in the main configuration screen, a standard htaccess.txt file is included in the package en needs to be renamed to .htaccess. With this option enabled URLs are made on the base of ID numbers like Domain-name/12/25/3/, but here you also want more… that is why you should install a SEF Component like sh404SEF that will give you much better URLs. And it will give you a good 404 error page that will also uses a proper 404 header. (Joomla standard will give an 200 OK and redirects you to the Homepage…)
• Title with the same SEF component you will get the opportunity to use the title alias function for you URL so you can use your normal article title for you optimization. For an optimal use of titles, and also for your menu items, you can use the SEF Patch of Joomlatwork , there is also a paid version that will give you a separate HTML Title option for more control like the WordPress SEO Title plugin.
• Metatags the description and keyword options are already in a standard Joomla incorporated for each article, but not for menu items, you will have to get the above mentioned SEF Patch to use that.

Tip: Choose with any SEF component you use alway the option /category/title and not /section/category/title to get a little shorter URLs. /title/ alone is also a possibility but not as good, because you can run into trouble like things like /Drupal/installation manual.HTML and /WordPress/installation manual.HTML (Drupal en WordPress are here been used as categories)

Joomla 1.5

• URL Rewrite is in Joomla 1.5 done with the SEO settings in your Global configuration, but you have now three options, unfortunately in each of those options, there is always an item ID number in the URL.
  • SEF on, will give you directly URLs with the title in it, but with index.php in the URL. (can also be used on windows hosting)
  • SEF with the use of .htaccess, this will also give you the URL with title, but than without the index.php
  • Use suffix, this options sets a .HTML at the end of your URL
  • Attention! Joomla 1.5 uses the title alias, but you have to set the “-” between the words in your URL options, otherwise you will get a %20% in your URL if you leave it blank.
• Title here Joomla will use the standard article title, if your want more control, than you can use the new Joomla 1.5 SEF patch from Joomlatwork.com (Dutchies ;-)) and I have to add here that Richard of Joomlatwork already has stated that the SEF patch will be update with each release until it is in the Joomla core!
  If you use the SEF patch you get an extra SEO tab in your configuration screen, don't forget to set the minimal [TITLE] option, otherwise your title will show your URL as title.
• Metatags are also like the “old” Joomla version built-in for articles and site wide via your Global configuration. But like with the old version, here is the same advice to get more control use the SEF patch of Joomlatwork.com .

Tip: For both versions of Joomla versions an advice, do not use the Global Metatag settings! With version 1.0.x you will get the text of the Globals on top of the page Metatags which will leave you with pretty much the same Metatags in the search engines as snippets, version 1.5 does this a lot better, and will not fill it with the standard if you use the page description.However is does set this if the page description is empty…

Conclusion: None of the three is out-of-the-box ready as search engine friendly Content Management system. With all three there needs to be done some extra work to realize the desired options.

For me they all have there own usage:

• WordPress works great for smaller websites and even bigger Blogs
• Joomla is fine for SMB websites and, with some extra extensions can be used for bigger sites as well.
  Especially the easy and user friendliness is great for less “technical” webmasters.
• Drupal can do almost everything, but for me is somewhat staying behind the others because of the lack of user friendliness for those who have the maintain and edit the page content.

But the most important factor in the choice of system is still what your customer wants and the ease of use for him/her… if the site has to become a success, then it must by their website, and to achieve that they have to be able to easily maintain the site themselves!
For search engine optimization…, well, that is why there are specialists, those who will look at the details… and each of them will have there own preferences for a certain system.

O yes, tips and  other options… the comments are open :-)